1. Field of the Invention
The present invention relates to an apparatus for recording a biological signal, an earthquake wave, a video signals, a voice signal and other types of signal, and, in particular, to a signal recording apparatus which, when instructed to start a signal recording, is capable of recording the necessary signal.
2. Description of the Related Art
A recording apparatus which uses magnetic tapes or recording disk media, such as magnetic disks and optical disks, serves as an external storage device for use in a data processing device or as a medium for recording, in real time, signals transmitted in one direction or unexpectedly-generated signals.
In general, it is not easy to select only a desired, arbitrary signal from those signals input in real time, and record it in real time. If, as with a telecast or radio broadcast, the telecast time is known in advance, the signal can be recorded at the telecast time; however, for recording a desired signal whose generation is not known in advance, it is not possible to pick up and record only that signal. With regard to a telecast program, for example, it is easy to record the entire program, but it is difficult to select only a specific scene or music from the program and record it from the beginning. Neither is it possible to completely record those signals such as earthquake wave or unusual cardio-wave signals whose generation is unpredictable or unexpected.
In order to record such an unexpectedly-generated signal, one can simply temporarily record all the signals input in real time and select only the desired portion later. However, such editing requires a vast amount of memory capacity for temporary storage, as well as a significant amount of effort. With an endless tape used for temporary storage, a relatively small amount of memory capacity is needed, but the signal-storable range is limited to the time in which the endless tape circulates. It is therefore not possible to record the entire signal generated over the period before and after the desired signal time.
A so-called past-data for use in a telephone, which records a conversation made by the operator a certain period of time prior to the present time, is also known. A conventional past-data recorder repeatedly updates the data recording in such a way that the most recent signal for a given time always remains in the IC memory and the replacement of the most recent signal stored as new data is stopped by data-save instruction to preserve and reproduce the content of the IC memory. This makes it impossible to record a signal coming after the reception of the data-save instruction in the same memory, and necessitates the use of another memory for recording the signal. Therefore, continuous signals are separately recorded in plural memories, so that in practice, specific editing is necessary to collect and store these signals in one memory. In order to record a sequence of signals in the same memory in real time, first the content of a first memory for recording of past data should be read out in response to a data-save instruction and should then be transferred to a second memory so that the first memory is again ready for recording. As a result, there would be an inability to record during the time required to transfer the content of the first memory to the second memory. According to the prior art, therefore, it is not possible to selectively record in real time only the desired one of a number of signals input in real time on a single recording medium, and a period exists during which recording cannot be executed.